In a typical solid oxide fuel cell generator configuration, a multiplicity of fuel cells are vertically mounted in a square pattern, and are electrically connected in series in the rows and in parallel in the columns of the pattern. Gaseous fuel is passed over the outside of the cells and an oxygen-containing gas is passed through the inside of the cells. Oxygen migrates through the cells as oxygen ions and burns the fuel, generating electricity and heat. Such generators are taught by Isenberg in U.S. Pat. No. 4,395,468 and Makiel in U.S. Pat. No. 4,520,082.
While most of the heat is removed by the flow of the gases, some heat is lost through the walls of the generator, causing the temperature in the center of the generator to be higher than the temperature at the periphery of the generator, especially at the corners. The presence of a large temperature gradient between the center of the generator and the periphery makes it more difficult to operate the generator within the optimal temperature range of about 800.degree. C. to about 1100.degree. C. As a result, temperatures at the center may exceed the optimum, resulting in a shorter cell life and the deterioration of materials, and temperatures at the periphery may fall below the optimum, resulting in inefficient cell operation and the loss of electricity. Efforts to solve this problem through the use of additional insulation have proved to be impractical or even counterproductive.